Method of and apparatus for producing power in remote locations

ABSTRACT

A system for producing power at remote locations comprises: a closed cycle vapor turbine unit having an evaporator containing liquid working fluid, a turbine receiving vapor of the evaporated working fluid for producing power by way of an electrical generator coupled to the turbine, a condenser and means for returning the working fluid condensate from the condenser to the evaporator; a biomass furnace associated with the evaporator for heating working fluid present in the evaporator and evaporating a portion of the working fluid; and a controller for controlling the amount of biomass fuel supplied to the biomass furnace in accordance with energy requirements of a customer load. Further, a method for producing power using the system is also provided.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method of and apparatus forthe operation of a closed cycle vapor turbine unit by biomass only, orcombined with solar energy, and more particularly, a method of andapparatus for the operation of a closed cycle vapor turbine based on anorganic Rankine cycle with biomass only or combined with solar energy.

[0003] 2. Description of the Prior Art

[0004] Many communities in remote locations are living on agricultureproducts. Such products in most cases are partially processed in thefields or near the farmer's home or in the village. There are largequantities of unused biomass wastes that remain to rot or decompose onsite.

[0005] At the same time, many of such rural communities are notconnected to the electric grid, but they need electrification to improvethe quality of life.

[0006] The present invention overcomes the above deficiencies by the useof units for remote operation which may not have enough biomass supplyfor continuous operation and utilize solar energy during the day andbiomass during the night or during periods of low solar radiation.

[0007] Many of the locations that require remote electrification are inthe region of intense solar radiation and the addition of the option ofutilization of solar energy as an alternatative contributes tosuccessful installation.

BRIEF SUMMARY OF THE INVENTION

[0008] The present inventive subject matter is drawn to a system forproducing power at remote locations comprising: a closed cycle vaporturbine unit having an evaporator containing liquid working fluid, aturbine receiving vapor of the evaporated working fluid for producingpower by way of an electrical generator coupled to the turbine, acondenser and means for returning the working fluid condensate from thecondenser to the evaporator; a biomass furnace associated with theevaporator for heating working fluid present in the evaporator andevaporating a portion of the working fluid; and a controller forcontrolling the amount of biomass fuel supplied to the biomass furnacein accordance with energy requirements of a customer load.

[0009] Preferably, the controller for controlling the amount of fuelsupplied to the biomass furnace further controls the amount of biomassfuel supplied to the biomass furnace also in accordance with a controlsignal from a buffer load connected to the output of the generator. Alsopreferably, the controller for controlling the amount of biomass fuelsupplied to the biomass furnace additionally controls the amount ofbiomass fuel supplied to the biomass furnace also in accordance with amonitored evaporator temperature. More preferably, the system includes asolar parabolic concentrating system for providing heat to the workingfluid

[0010] The present inventive subject matter is further drawn to a methodfor producing power in remote locations comprising the steps of:providing a closed cycle vapor turbine unit having an evaporatorcontaining liquid working fluid, a turbine receiving vapor of theevaporated working fluid for producing power by way of an electricalgenerator coupled to the turbine, a condenser and means for returningthe working fluid condensate from the condenser to the evaporator;heating the working fluid present in the evaporator and evaporatingportion of the working fluid using a biomass furnace associated with theevaporator; and controlling the amount of biomass fuel supplied to thebiomass furnace in accordance with energy requirements of a customerload.

[0011] Preferably, the step of controlling the amount of biomass fuelsupplied to the biomass furnace further includes the step of controllingthe amount of biomass fuel supplied to the biomass furnace also inaccordance with a control signal from a buffer load connected to theoutput of the generator. Also preferably, the step of controlling theamount of biomass fuel supplied to the biomass furnace additionallyincludes the step of controlling the amount of biomass fuel supplied tothe biomass furnace also in accordance with a monitored evaporatortemperature. More preferably, the method includes the step of providingheat to the working fluid using a solar parabolic concentration system.

[0012] Three options of operation with solar and two intallations ofbiomass are brought up here as magor installation examples althoughadditional features can be added which are not the issues of the presentproposal such as use of heat recovery by recuperators after thecondenser etc.

[0013] A closed cycle vapor turbine (CCVT) unit is based on an organicRankine cycle and comprises an evaporator, turbine, condenser andcirculation pump.

[0014] Heat is supplied to the evaporator that is filled with organicfluid. The organic liquid temperature and pressure rises and part of theliquid is evaporated and flows out at the top of the evaporator. Aturbine that is installed on the vapor path will utilize the energy ofthe expanding vapors, thus operating a generator for the generation ofelectric power.

[0015] A droplet separator is preferably installed at the vapors exitpath to collect any liquid droplets that may enter the high pressureflow path, reach the turbine and damage the blades.

[0016] The expanding vapors, after expanding through the turbine, arecondensed in a water or air-cooled condenser in which the pressure islower according to the condensation temperature.

[0017] The condensed liquid is collected below the condenser and ispumped back to the evaporator to repeat the cycle. The liquid may bepumped by a mechanical driving force, turbine shaft-bearing centrifugalforces or gravity.

[0018] It is common practice to keep the cycle that uses organic fluidclosed, for fear of losing material and air pollution because of thenature of such liquids.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Embodiments of the present inventive subject matter are describedby way of example and with reference to the accompanying drawingswherein:

[0020]FIG. 1 is a schematic diagram of one embodiment of the apparatusof the present inventive subject matter.

[0021]FIG. 2 is a schematic diagram of another embodiment of the presentinventive subject matter.

[0022]FIG. 3 is a schematic diagram of still another embodiment of thepresent inventive subject matter.

[0023]FIG. 4 is a schematic diagram of a yet further embodiment of thepresent inventive subject matter.

[0024]FIG. 5 is a schematic diagram of a yet still further embodiment ofthe present inventive subject matter.

[0025]FIG. 6 is a block diagram of another embodiment of the presentinventive subject matter.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Two types of systems are presented here, but in both cases thebiomass furnace is directly heating the organic liquid. The differencebetween the two cases is that in one case, solar energy is introduced byway of a thermal fluid while in the other the organic fluid is alsodirectly heated by the solar energy.

[0027] An additional option is shown in FIG. 2 in which the flue gas isoptionally turned back to the biomass feeding silo to help dry thebiomass, thus increasing the furnace combustion efficiency since biomassmay contain high moisture levels that would reduce the heat value of thefuel if it was not dried before combustion.

[0028] An expansion tank is shown in both cases; however, in the case ofusage of thermal fluid some means for fluid expansion and short or longterm storage is a technical necessity due to the large difference in thefluid temperature between non-heated or heated modes, but in the case ofdirect heating of the organic liquid the evaporator itself can serve asthe expansion tank, but the additional tank shown may serve as storagein cases when solar heat is available and there is no immediate need forelectricity.

[0029] The following should be pointed out. A single controller cancontrol all operation modes. Solar energy is continuously connectedduring the day or if the expansion or storage tank has a high enoughlevel of stored energy. Biomass is used automatically to help theevaporator achieve evaporation temperature or supply energy to thebuffer. In the case of buffer load control, the buffer load is connectedto the power outlet of the turbine generator before the connection tothe customer loads. When the buffer load is empty, due to customer'suse, for example, the furnace receives a signal to increase the biomassflow and when the buffer load is full, the furnace receives a signal todecrease the biomass flow. In the case of temperature related control,the controller monitors the evaporator temperature and controls the fuelsupply accordingly. The rate of fuel is controlled by the temperaturedifference between the boiler instantly monitored temperature and thedesired temperature.

[0030] Air supply is controlled and optimized by an oxygen sniffer inthe furnace exit, or preferably in the boiler exit, i.e., the chimneyside. Small battery storage is necessary for start-up; large batterystorage is optional.

[0031] In the case of solar operation, which is optional, a flash traymay be introduced into the evaporator to improve flashing of the solarheated liquid and the liquid level may be modified during such modeand/or use of different inlet tubes operated by the controller.

[0032] In case flue gas is used for drying of biomass fuel, the lid ofthe supply silo must be equipped with a safety relief valve to let ofextra pressure created by the steam produced in the silo container—suchdrying will not only provide improved fuel to the combustion chamber,but also create higher pressure in the feeding compartment, thusreducing the chances for return fire from the furnace to the fuel silo.

[0033] In case the unit is vertical and high-condensed organic liquidreturns to the evaporator by gravity, part goes directly and the otherpart goes through the turbine bearing to lubricate it. In the case of alow unit-horizontal design unit, the turbine shaft rotation in thebearing produces pressure that pushes the lubricating liquid (theorganic fluid) through designed peripheral holes in the housing to adownstream tank that can be the evaporator.

[0034] Referring now to FIG. 6 describing the operation of thebiomass-fueled power unit, The systems are capable of supplying therequired power output from zero to the maximum rated power output. Inorder to do this, the system identifies the desired power output andcontrols the furnace to supply the required thermal energy to producethis power output, by doing so the system uses only the biomassquantities required and saves large amounts of biomass.

[0035] This is accomplished with the help of a buffer load, preferablyusing a Pulse Width Modulator (PWM) which is connected to the poweroutlet of the turbine generator before the connection to the customerloads. When the buffer is empty, due to customer's use, for example, thefurnace receives a signal to increase the biomass flow, and when thebuffer is full, the furnace receives a signal to decrease the biomassflow.

[0036] The furnace is able to operate at thermal loads of 20% of themaximum load with desired ratio between the biomass flow and the airsupply for efficient combustion. Air supply is controlled and optimizedby an oxygen sensor in the furnace exit or preferably in the boiler exitside, i.e., chimney side.

[0037] The controller establishes the desired furnace output and sendsfurnace output and sends a linear signal to the furnace and to the airblower. The air supply to the combustion influences the oxygen level inthe exhaust gases, the feeder supplies the required biomass to enablecombustion with the desired air/fuel ratio. The air/fuel ration setpoint changes according to the power demand from the boiler, to optimizethe furnace performance.

[0038] The operation of the system starts with power supply to thefurnace and to the control system from a battery, when the turbine isturning, the generator charges the battery and disconnects the batteryfrom the system. From here on, the furnace receives the power itrequires from the turbine generator. In case of planned use of batterystorage, the rate of produced power that will be used for charging fromthe total production can be controlled by the controller.

[0039] The system recognizes customer's request according to the bufferload condition, when the buffer load is full, the system will connectthe customers and decrease the request from the furnace. When the bufferload is empty, the furnace receives a signal to work at full load andthe customers are connected automatically only when the buffer load isfull.

[0040] The inventive subject matter being thus described, it will beobvious that the same may be varied in many ways. Such variations arenot to be regarded as a departure from the spirit and scope of theinventive subject matter, and all such modifications are intended to beincluded within the scope of the following claims.

1. A system for producing power at remote locations comprising: (a) aclosed cycle vapor turbine unit having an evaporator containing liquidworking fluid, a turbine receiving vapor of the evaporated working fluidfor producing power by way of an electrical generator coupled to saidturbine, a condenser and means for returning the working fluidcondensate from the condenser to the evaporator; (b) a biomass furnaceassociated with said evaporator for heating working fluid present in theevaporator and evaporating a portion of said working fluid; and (c) acontroller for controlling the amount of biomass fuel supplied to saidbiomass furnace in accordance with energy requirements of a customerload.
 2. A system for producing power according to claim 1 wherein saidcontroller for controlling the amount of fuel supplied to said biomassfurnace further controls the amount of biomass fuel supplied to saidbiomass furnace also in accordance with a control signal from a bufferload connected to the output of said generator.
 3. A system forproducing power according to claim 2 wherein said controller forcontrolling the amount of biomass fuel supplied to said biomass furnaceadditionally controls the amount of biomass fuel supplied to the biomassfurnace also in accordance with a monitored evaporator temperature.
 4. Asystem for producing power according to claim 2 wherein said buffer loadcomprises a pulse width modulator.
 5. A system for producing poweraccording to claim 1 including an oxygen sensor located at the exit ofsaid evaporator for controlling the air/fuel ratio in the biomassfurnace.
 6. A system for producing power according to claim 1 whereinsaid working fluid is an organic fluid.
 7. A system for producing poweraccording to claim 1 wherein said means for returning the working fluidfrom the condenser to the evaporator comprises a pump.
 8. A system forproducing power according to claim 1 further comprising a line forsupplying flue gases exiting said evaporator to biomass fuel for dryingsaid biomass fuel.
 9. A system for producing power according to claim 1further comprising a solar parabolic concentrating system for providingheat to the working fluid.
 10. A method for producing power in remotelocations comprising the steps of: (a) providing a closed cycle vaporturbine unit having an evaporator containing liquid working fluid, aturbine receiving vapor of the evaporated working fluid for producingpower by way of an electrical generator coupled to said turbine, acondenser and means for returning the working fluid condensate from thecondenser to the evaporator; (b) heating said working fluid present inthe evaporator and evaporating portion of said working fluid using abiomass furnace associated with said evaporator; and (c) controlling theamount of biomass fuel supplied to said biomass furnace in accordancewith energy requirements of a customer load.
 11. A method according toclaim 10 wherein the step of controlling the amount of biomass fuelsupplied to said biomass furnace further includes the step ofcontrolling the amount of biomass fuel supplied to said biomass furnacealso in accordance with a control signal from a buffer load connected tothe output of said generator.
 12. A method according to claim 11 whereinthe step of controlling the amount of biomass fuel supplied to saidbiomass furnace additionally includes the step of controlling the amountof biomass fuel supplied to said biomass furnace also in accordance witha monitored evaporator temperature.
 13. A method according to claim 11wherein the step of controlling the amount of biomass fuel supplied tosaid biomass furnace also in accordance with a control signal from abuffer load connected to the output of said generator is carried outusing a pulse width modulator.
 14. A method according to claim 10including the step of controlling the air/fuel ration in the biomassfurnace using an oxygen sensor located at the exit of said evaporator.15. A method according to claim 10 including the step of using anorganic fluid for the working fluid.
 16. A method according to claim 10wherein flue gases exiting said evaporator are used to dry the biomassfuel.
 17. A method according to claim 10 further including the step ofproviding heat to the working fluid using a solar parabolicconcentration system.